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Chapter Nine:

COVALENT BONDING:

ORBITALS

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Contentsp390

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9-1 Hybridization and the LocalizedElectron Model

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sp3 Hybridization

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Draw the Lewis structure for hydrogen

fluoride.

What is the shape of a hydrogen fluoride

molecule?

React 1

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sp3 hybridizationp391

Figure 9.1 The Lewis structure of the moecle. (b) Thetetrahedral molecular geometry of the methane molecule.

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Why can’t the bonding orbitals for methane be

formed by an overlap of atomic orbitals?

React 2

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Figure 9.2

The valence orbitals on a free carbon atom:2s, 2px, 2py, and 2pz.

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Figure 9.3

The formation of sp3 hybrid orbitals p392

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Cross section of an sp3 orbital. This shows a “slice”

of the electron density of the sp3 orbitals illustrated in

the center diagram fig. 9.3.

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Figure 9.4

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Figure 9.5

An energy-level diagram showing theformation of four sp3 orbitals

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Tetrahedral set of four sp3 orbitalsp393

Figure 9.6

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sp3 Hybridization

Ex 9.1 The Localized Electron Model P393

Describe the bonding in the ammonia using

the localized electron model.Solution

A complete description of bonding involves threesteps:

1. Writing the Lewis structure

2. Determining the arrangement of electron pairsusing the VSEPR model

3. Determining the hybrid atomic orbitals need todescribe the bonding in the molecule

The Lewis structure for NH3 is

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Why can’t sp3 hybridization account for the

oxygen molecule ?

React 3

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sp2 Hybridization

Figure 9.8 The hybridization of the s, px, and py atomic orbitals

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An Orbital Energy-Level Diagramfor sp2 Hybridization

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Figure 9.9

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Formation of C=C Double Bond in Ethylenep395

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sp2 Hybridization

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Figure 9.14 When one s orbital and one p orbitalare hybridized, a set of two sp orbitals oriented at180 degrees results.

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The sp orbitals of carbon in carbon dioxide are used to formthe σ bonds between the carbon and the oxygen atoms.

Figure 9.15 The hybrid orbitals in the CO2 molecule.

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The orbital energy-level diagram of CO2

Figure 9.16 The orbital energy-level diagram for theformation of sp hybrid orbitals on carbon.

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sp Hybridization

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The orbitals for CO2p397

Figure 9.19 (a) The orbitals used to form the bonds in carbondioxide. Note that the carbon-oxygen double bonds consist ofone σ bond and one π bond. (b) The Lewis structure forcarbon dioxide.

P397Ex 9.2 The Localized Electron Model IIDescribe the bonding in the N2 molecule.

Solution:

The Lewis structure or the nitrogen molecule is : N≡N:

Figure 9.20

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dsp3 hybrid orbitals p398

P398Ex 9.3 The Localized Electron Model IIIDescribe the bonding in the triiodide ion (I3-)

Solution:

The Lewis structure for I3-

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The orbitals used to form the bonds in PCl5

Figure 9.22

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d2sp3 Hybridization p399

P400Ex 9.4 The Localized Electron model IV

How is the xenon atom in XeF4 hybridized?Solution:

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The localized Electron Model: A Summary

Localized Electron Model1. Draw the Lewis structure

2. Determine the arrangement of electrons

pairs using the VSEPR

3. Specify the hybrid orbitals needed too

accommodate the electron pairs

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Figure 9.24 The relationship of the number of effective pairs,their spatial arrangement, and the hybrid orbital set required.

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3

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Figure 9.24 (continued)

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P401Ex 9.5 The Localized Electron model IV

For each of the following molecules or ions, predict

the hybridization of each atom, and describe the

molecular structure.

a. CO b. BF4- c. XeF2

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The Localized Electron Model

Draw the Lewis structure(s)

Determine the arrangement of electron pairs

(VSEPR model).

Specify the necessary hybrid orbitals.

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9-2 The Molecular Orbital Model

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Bonding in H2

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Sigma Bonding and Antibonding Orbitals

Figure 9.25

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H2 Bond order =2

02H2

-=1 Bond order =

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Pi Bonding and Antibonding Orbitals

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Molecular Orbital Diagramfor the N2 Molecule

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Magnetic Properties of LiquidNitrogen and Oxygen

p4069-3 Bonding in Homonuclear DiatomicMolecules

The bonder for Li2 is 12

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Figure 9.33 (a) The three mutually 2p orbitals on two adjacentboron atoms. The signs indicate the orbital phases. Two pairs ofparallel p orbitals can overlap, as shown in (b) and (c), and the thirdpair can overlap head-on, as shown in (d).

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Figure 9.34

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Apparatus used tomeasure theparamagnetism ofa sample

Figure 9.37

p409Paramagnetism

Figure 9.38 Correctmolecular orbital energylevel for B2 molecule.

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Ex 9.6 The molecular Orbital Model I P410

For the species O2, O2+, and O2

-, give the electron

configuration and bond order for each. Which has the

strongest bond?Solution:

Figure 9.39

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P411Ex 9.7 The molecular Orbital Model II

Use the molecular orbital model to predict

the bond order and magnetism of each of

the following molecules.

a. Ne2

b. P2

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9-4 Bonding in Heteronuclear DiatomicMolecules

Ex 9.8 The Molecular Orbital Model IIIUse the molecular orbital model to predict the magnetism

and bond order of the CN- ions.

Bond order: 33

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Solution:

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Orbital energy-level diagram for the HFmolecule

Figure 9.43

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The electron probability distribution in thebonding molecular orbital of the HF molecule

Figure 9.44

9-5 Combining the Localized Electronand Molecular Orbital Models

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The sigma system for benzene

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The pi system for benzene

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Pi Bonding in the Nitrate Ion